[PATCH v4 5/5] arm64/kernel: enable A53 erratum #8434319 handling at runtime

[Mark Rutland]

On Thu, Mar 08, 2018 at 01:46:34PM +0000, Ard Biesheuvel wrote:
> On 8 March 2018 at 13:45, Will Deacon <will.deacon at arm.com> wrote:
> > On Tue, Mar 06, 2018 at 05:15:35PM +0000, Ard Biesheuvel wrote:
> >> Omit patching of ADRP instruction at module load time if the current
> >> CPUs are not susceptible to the erratum.
> >
> > [...]
> >
> >> diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c
> >> index 534bf1d47119..1a583ccace00 100644
> >> --- a/arch/arm64/kernel/module-plts.c
> >> +++ b/arch/arm64/kernel/module-plts.c
> >> @@ -158,7 +158,8 @@ static unsigned int count_plts(Elf64_Sym *syms, Elf64_Rela *rela, int num,
> >>                       break;
> >>               case R_AARCH64_ADR_PREL_PG_HI21_NC:
> >>               case R_AARCH64_ADR_PREL_PG_HI21:
> >> -                     if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_843419))
> >> +                     if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_843419) ||
> >> +                         !cpus_have_const_cap(ARM64_WORKAROUND_843419))
> >>                               break;
> >>
> >>                       /*
> >> diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
> >> index 89217704944e..47b40aaa1a5d 100644
> >> --- a/arch/arm64/kernel/module.c
> >> +++ b/arch/arm64/kernel/module.c
> >> @@ -201,6 +201,7 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
> >>  static int reloc_insn_adrp(struct module *mod, __le32 *place, u64 val)
> >>  {
> >>       if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_843419) ||
> >> +         !cpus_have_const_cap(ARM64_WORKAROUND_843419) ||
> >
> > Mind if I drop the IS_ENABLED check here and in the hunk above? The
> > const_cap check along should be sufficient, no?
> >
> 
> Without the IS_ENABLED() check, the code will always be present in the
> object file.
> 
> I have no strong preference either way, though.

As with other case, perhaps fold this into a helper in
<asm/cpufeature.h> ?

static inline bool system_needs_arm64_workaround_843419()
{
	return (IS_ENABLED(CONFIG_ARM64_ERRATUM_843419) &&
		cpus_have_const_cap(ARM64_WORKAROUND_843419))
}

... then use the inverse in the cases above.

Thanks,
Mark.